<!DOCTYPE html>
<html>

<head>
    <title>Lots of Iframes</title>
</head>

<body>
    <script>
        for (let i = 0; i < 30; i++) {
            const iframe = document.createElement('iframe');
            iframe.srcdoc = `
This is IFrame ${i}.
<input type='checkbox' id='checkbox${i}'>
`
            document.body.appendChild(iframe);
        }
    </script>
</body>

</html>
